Dynamics of the orientation of active and passive scalars in two-dimensional turbulence
Dynamics of the orientation of active and passive scalars in two-dimensional turbulence
复制标题
二维湍流中主动和被动标量方向的动力学
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
P. Klein
中科院分区：
文献类型：
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作者：
G. Lapeyre;B. Hua;P. Klein
研究了涡度的主动性质，以了解它与被动标量的区别。在自由衰减二维（2D）湍流的数值模拟中，通过经典和新的诊断（基于示踪剂梯度特性）来检查直接级联到小尺度。在湍流的瞬态演化过程中，被动标量由于与Lapeyre等人在绝热近似中得到的平衡取向不同的排列性质而具有更强的级联。[j].地球物理学报，1999,16(2):1 - 4。在应变主导区域，被动标量梯度比涡度梯度更符合平衡取向，而在有效旋转主导区域则相反。运动学对齐特性的研究表明，这是由于结构与封闭流线在后一区域。然而，在湍流的最终演化阶段，主动和被动示踪剂梯度都具有相同的取向（即两个梯度之间存在完美的对准，当它们更强时更是如此）。研究了扩散对叶栅的影响。
The active nature of vorticity is investigated in order to understand its difference with a passive scalar. The direct cascade down to small scales is examined through both classical and new diagnostics (based on tracer gradient properties) in numerical simulations of freely decaying two-dimensional (2D) turbulence. During the transient evolution of turbulence, the passive scalar possesses a stronger cascade due to different alignment properties with the equilibrium orientations obtained in the adiabatic approximation by Lapeyre et al. [Phys. Fluids 11, 3729 (1999)] and Klein et al. [Physica D 146, 246 (2000)]. In strain-dominated regions, the passive scalar gradient aligns better with the equilibrium orientation than the vorticity gradient does, while the opposite is true in effective-rotation-dominated regions. A study of the kinematic alignment properties shows that this is due to structures with closed streamlines in the latter regions. However, in the final evolutionary stage of turbulence, both active and passive tracer gradients have identical orientations (i.e., there is a perfect alignment between the two gradients, all the more so when they are stronger). The effect of diffusion on the cascade is also studied.